Emissions - bad cat?

[LFogelson]

I brought my stock exhaust 82 SC to the wrench to adjust the CO mixture prior to my smog test. I previously fixed intake leaks and readjusted the mixture by smell/power/idle. It turned out I was close. The numbers looked good, car ran well. Went to the Smog test and failed CO=2.0 (1.2 to pass). The meter at my wrench showed CO=0.6 (precatalytic) and HC & CO2 within limits. Incidently, the O2 sensor connector wire broke. But the numbers were still fine without the sensor. I talked to the wrench after the test and he said my Catalytic Converter is probably bad. We probably should have checked the CO with his meter at the tail pipe. I am thinking about gutting the cat and trying again. Maybe eventually I'll switch to a premuffler if I pass the emissions. Where I live it is a pain to find someone with a CO tester - everyone says after their old ones break they don't fix them because most newer cars can be tested off their computer. Opinions?

[Lorenfb]

First, does your state use a dyno, like most, at 15 mph and 25 mph?
If so, then you probably need the O2 system to work. You need to
check the CO at 2000 rpms versus just at idle.

You indicate that the CO at idle is .6% before the CAT which means
it's less after the CAT. The CAT has the greatest effect on the NOx
and less on the CO and HCs. If your CO with the O2 working (at
2000 rpms) is less than 1%, then you'll probably have no problem
passing the test on a dyno if required.

More than likely, the CAT is O.K. Don't waste money on a new one
unless you're sure it needs one.

Good Luck
Loren
'88 3.2

[john70t]

It depends on whether or not the car sat, was started cold, quickly reved, and way out out of specs to begin with. Other things are bad gas, extended idling, and oil that needs changing.

Testing the CO levels(which=fuel mixture) before and after the cat will tell you if it's working or not. A hole can be drilled and rivited to achieve this if necessary... A lazer thermometer(I've been told) on a good working hot cat will show at least 100 degrees temp difference between the two which means the platinum/paladium inside is burning up the HC's.
Changing intake/exhaust systems and removing the cat may cause a headache if the tech knows what he's doing. Staying stock and well maintained is best.

[LFogelson]

Can a bad catalytic converter raise your CO? Is my wrench's analyzer miscalibrated?
I was considering hollowing out my converter if it is raising my CO.
Because of the age of my car the test is at idle (no dyno) after "Pre" revving for 85 sec at 2500 rpm. My car did idle for a while prior while waiting in the line for the test.

[CarreraS2]

I don't think a bad cat can RAISE your CO.

The cat is mainly for NOx. Even without a cat, a 911 can usually pass the stringent Calif. CO test WITHOUT a cat, if the car is tuned right.

I don't think your problem is your cat.

[Lorenfb]

I agree with SoCal911SC:

1. the CAT with not raise your CO
2. a well tuned 911 will usually pass w/o a CAT
3. the CAT is not you problem

As I said before, you need to get the Lambda system (O2) to work.
Also, you need to run the engine at 2000 RPMs and check the CO
at 2000 RPMs, and if necessary adjust the CO there.

Good Luck
Loren
'88 3.2

[sammyg2]

IMO your cat is fine. Your HC levels are acceptable so that usually rules out the cat. In order to lower your CO levels you either have to lean it out a bunch more or hook up your O2 sensor.

If you have a small vacuum leak you can adjust the mixture at idle and it will be fine, but it will go rich when throttle is applied as the amount vacuum leak gets smaller as a percentage of total air flow.

[dvkk]

Originally posted by LFogelson
Can a bad catalytic converter raise your CO? Is my wrench's analyzer miscalibrated?

What probably happend was when your wrench was taking his measurement, oxygen was being pulled into the exhaust, diluting the reading. He needs to figure out a way to seal the probe in the exhaust to prevent the dilution. I have this problem all the time when my car is tested. My short tail pipe has a bend in it about 8-10" from the tip, and the testing station's probes are rigid and straight, so they can't go in far enough to avoid an oxygen dilution error.
There is no way the CO can increase after it leaves the combustion chamber.

[sliminbay]

I been heavily involved with the dyno smog check in northern california and if any mechanic tells me something is wrong before fixing the obvious problem, I would run like hell out of his shop. It's against the CA law for the advise the wrnech gave you on your car. You have bad O2 wire that needs to be fixed before your DME will start to adjust your air/fuel ratio. Maybe you want to let the board know which shop it is so that people stay away from this crook. So tired of bad mechanics blaming everything on CAT or O2 sensor.

[LFogelson]

Thanks for all the advice.
My wrench told me it is definately better to run with the 02 sensor connected and to resolder the connector wire. However, he was surprised it failed running open loop because the numbers at IDLE did not change from the adjusted value after the wire broke. He never checked at 2000rpm. Further I bet an air leak at the test probe insertion is a great explanation. I saw him have to move the probe a couple of times to get a reading other than "NO FLOW."
I will definately leave my cat alone. Now the question is should I resolder the 02 connector and retest ($14). Or should I try and readust the fuel mixture. I guess I can check my plugs to see if they look black. Thanks again. Happy New Year.

[john70t]

I was planning on getting smog certified in CA at one point and took some classes on it.

On of the official CARB b.s. things we were taught was that if the tech finds something obviously wrong(i.e. vacuum hose cracked, he is not supposed to tell the customer about an easy or any fix.
Rather, he enters "defective" on the pass/fail list so your plate goes to the DMV.

The DMV get their numbers and show the feds their program is working and the next year California gets their highway dollars even though emmisions have gone up and they still can't sell an electric car worth a damn(except Honda who did it al by themselves).

The tech who fails your car then writes you an expensive estimate which you the stupid consumer have to pay. They win, you lose. The enforcement is only determined by whos in office and how badly in debt the state is.

I even had a gold-shield smog shop (Marathon on El Camino in Milbrae) tell me I needed a $45 fix to pass smog. When showed him my ASE master mechanic certification and questioned him further, he showed me a 6" piece of vacuum hose that was slightly kinked, said it wasen't a problem, and sweating profusely wished me a good day.


LFogelson: connect the O2, make sure the ignition parts are good, put some techron in it, drive it for a couple hours at a consistent high RPM, change the oil and take it back hot to get tested under "operator training mode". If it passed before, it should pass again.